With the rapid development of science and technology and industrial production, energy resource and the environment increasingly attract whole social attention with higher demands for energy saving and environmental protection. Regarding to energy consumption, energy consumption from buildings accounts for nearly 40% of the total social energy consumption, of which the energy loss through the glass doors and windows in the building energy consumption reaches more than 50%, that is, the glass doors and windows has become the largest energy vulnerability of buildings. The main energy consumption within the building is due to heating and air conditioning. Improving windows heat insulation performance is an effective way to reduce building energy consumption. Energy saving performance of architectural glass, has become the key to achieve energy saving in buildings. To achieve energy-saving in architectural glass, the sunlight through the glass has to be controlled.
More than 99% of solar radiation spectrum is at the wavelength range of 0.15 to 4.0 μm. About 50% of solar radiation energy is in the visible region of the spectrum (wavelength of 0.4 to 0.76 μm), 3% in the ultraviolet (UV) spectral region (wavelength of <0.38 μm), 47% in the infrared (IR) region of the spectrum (wavelength of >0.76 μm), which near-IR ray is known as hotline. However, maximum transmittance of ordinary glass happens to be in the region of the solar radiation spectrum, meaning that its sunlight transmission is not influenced. It is necessary to achieve heat insulation and energy-saving in the constructions, automotive and ships through the glass coated sunlight control coating or film, thus saving energy for heating and air conditioning. Sunlight control refers to regulation of different wavelengths and heat energy of sunlight through glass products accessing to certain spaces (buildings, cars or ships internal). Apparently, under the premise without affecting space lighting, blocking and absorbing of UV and IR and reducing thermal radiation rate are effective ways to control sunlight. UV does not account for a large proportion in energy, but greatly harmful to the surface paint of furniture and human bodies, which is one of the reasons that anti-UV glass has been increasingly widely used. On the one hand, by reducing solar energy through sunlight control can obtain reduction of heat flux of accessing to certain space (building, car or ship), so that the space inside will keep cool, thus to reduce the need for air conditioning, finally to achieve purposes of energy saving and environmental protection. On the other hand, by reducing the heat radiation, the glass can become medium and far IR reflector, to reduce the heat flux through the glass outwardly, thereby reducing air conditioning requirements and the cost, to achieve the purpose of energy saving. improving window insulation performance by effective low thermal radiation coating can improve interior comfort in summer and winter.
For sunlight control and low thermal radiation properties and commercially acceptable coated glass article, the manufacturing considerations are cost, life and capabilities of maintaining the relative performances (solar transmittance, visibility, colour, transparency, and the shielding factor). Currently, methods for the preparation of coated glass for sunlight control and low thermal radiation are mostly magnetron sputtering, PVD, CVD coating and the thermal spray coating. Specifically, the additives which are against or absorb UV and IR, through the above methods, sputter or coat onto the glass to achieve effective control of sunlight into the room. Equipment prices by using above methods are expensive with restrictions on the substrate and the substrate shape, size. Furthermore, the methods are difficult to apply to existing glasses, therefore meeting a very limited commercial promotion. At present, coated glasses are mainly used in automotive, which market is basically monopolized by very expensive films from companies of the United States 3M, V-BEST, JOINNS, JOHNSON, and difficult to be extended to architectural glass.
Without aging concern, inorganic nano-additives can be used permanently, while organic additives usually aging with a life period. Therefore, commercial applications with inorganic additives is growing. Commercial inorganic additives with UV-blocking property are metal oxides, such as zinc oxide, titanium oxide and cerium. IR-blocking metal oxides are antimony tin oxide (ATO) and indium tin oxide (ITO). Another commercial inorganic additive absorbing IR is lanthanum hexaboride. In recent years, the rise of the glass insulation coating or film, are increasingly focused on the use of the metal oxide as an additive.
Ideally, the particles in the glass coating or film matrix must be less than the nominal particle diameter of 100 nm, in order to maintain the transparency and pellucidity of the original glass. This is one of the main reasons that nanotechnology draw attentions in this area. In addition, the metal oxide nano-particles in the coating or film will not form a conductive film, therefore do not interfere with operation of the radiation transmitting and receiving devices within the protective structure glazing.
In the preparation of functional metal oxide dispersion, it is necessary to mix at least two sorts of metal oxide nano-particles with blocking UV or IR property in dispersions. The traditional method is to disperse metal oxide particles in certain solvent with some dispersant by ball milling or sanding milling. This simple powder reprocessing approach may cause serious aggregation, especially due to the high surface energy of nano-particles. Moreover, the uneven intensity of ball milling or sanding milling may lead to non-uniform secondary particle size of the dispersed particles; in addition, ball milling and sanding milling inevitably introduce impurities. Dispersion and the modification belonging to physical modification methods, affecting the stability of functional dispersion, which is difficult to maintain the particles in the dispersion in nanoscale and keep stable for long time. These will affect the application of the functional dispersion, ultimately affect the transparency and other properties of the glass coating or film.
Therefore, there is a need to develop tin-containing metal oxide nano-particles and their dispersions which are economically viable, high transparent and blocking UV and IR, able to use in the glass coating and film with good dispersion stability, overcome or ameliorate the above mentioned disadvantages.
Therefore, there is a need to invent a preparation method of tin-containing metal oxide nano-particles and their dispersions which are economically viable, high transparent and blocking UV and IR, able to use in the glass coating and film with dispersion stability, and overcome or ameliorate the above mentioned disadvantages.